Turbo-molecular vacuum pumps are well known to the person skilled in the art. Such pumps comprise a mechanism suited to pump gases at high vacuum pressures, including rotor and stator components each having blades extending radially from an axis. At high vacuum pressures the gas molecules behave in a molecular flow regime.
It can be advantageous to locate rotor bearings at each end of the rotor shaft, depending on the application that the pump is designed to serve. Thus, the rotor can be supported in a way that minimizes rotor movement during operational conditions. As a result, the bearing located on the rotor shaft nearest to the pump inlet is located in an area of high vacuum pressure.
In certain circumstances it may been necessary to use non-contacting bearings in this location in order to minimize contamination that might be caused by bearing lubricant. Such non-contacting bearings include magnetic bearings that can configured as passive magnetic bearings or active magnetic bearings. In all cases, the bearings located at the pump inlet side of the rotor are located on the rotor's axis and coupled to the pump body by a series of spokes extending from a central bearing support hub. Thus, the bearing is secured in the desired position coaxially with the axis of the rotor and/or drive shaft. The spoke and hub arrangement can be called a “bearing spider”; this arrangement for supporting the bearing resembles a spoked steering wheel used in automotive vehicles, typically having an outer circular rim and a central boss connected to the rim by three or more equally spaced spokes.
A typical turbo-molecular pump bearing system is disclosed in DE202013009660U1 where the bearing spider is a separate component that is inserted into the pump. An outer rim of the bearing spider is arranged to engage with the pump body to secure a passive magnetic bearing in the correct central location. A similar arrangement is disclosed in US2003/0170132. In both these documents, the bearing spider is shown as a separate component that is located in position during pump assembly.
It is also known to provide the bearing spider as a component that is integral with the pump body. Such arrangements are known from pumps sold by Pfeiffer Vacuum GmbH, such as the Hipace 80 and Hipace 300 pumps. Additionally the EXT555 vacuum pump sold by Edwards Limited has a similar arrangement. In this integral configuration the spokes of the bearing spider extend in a generally radial direction from the inner section of the pump's inlet flange towards the central hub. The pump body and bearing spider can be machined from the same block of material, thereby reducing the number of component parts. Furthermore, this integral configuration for the bearing spider has other advantages in that the number of assembly steps can be reduced, tolerance stack-up can be reduced, the length of the pump can be reduced and controls on the bearing assembly process can be improved.
There is a general desire to improve the performance of turbo-molecular pumps that have a bearing spider on the high vacuum side of the rotor where the bearing spider is an integral part of the pump body. Furthermore, there is a desire to reduce the size and power consumption of such vacuum pumps without reducing the performance parameters of the pump.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter. The claimed subject matter is not limited to implementations that solve any or all disadvantages noted in the background.